The present disclosure is directed to wireless communications, including grant-free transmission schemes in multiple access systems.
Wireless networks such as long-term evolution (LTE) networks often utilize shared data channels for uplink (UL). The selection of a shared data channel for uplink (UL) is typically scheduling/grant based, and the scheduling and grant mechanisms are controlled by a base station (BS) in a network. A user equipment (UE) sends an UL scheduling request to the base station. When the BS receives the scheduling request, the BS sends an UL grant to the UE indicating its UL resource allocation. The UE then transmits data on the granted resource.
The signaling resource overhead for scheduling/grant mechanisms can be quite large, especially in cases where the data transmitted is small. For example, small packet transmissions of around 20 bytes each may use scheduling/grant mechanism resources that are around 30% to 50% of the packet's size. Scheduling/grant procedures may also cause an initial delay in data transmission. There is often a minimum delay of 7-8 ms in a typical wireless network between a scheduling request being sent and the first uplink data transmission.